Sales in that category grew 754% in the second quarter ended June 30, 2015, according to analysts at Morgan Stanley. That's up from a 296% growth rate in the first quarter of the year.

Morgan Stanley Research

Under Armour's "basketball footwear category growth has been very strong and likely helped by the success of NBA MVP Stephen Curry," analysts wrote. "This growth was higher than expected and can help push the stock higher since UA is showing it can compete in a category dominated by Nike, whereas Adidas seems to be retreating. This bolsters the view that UA's total addressable market is very big and bigger than thought just last year."

The shoe is sold out of most sizes on Under Armour's website. And it's gaining some attention from the elusive "Sneakerheads," an important faction of basketball fans who determine what's cool in athletic footwear.

The Curry One basketball shoe.
Under Armour
But Under Armour still has a long way to go.

"Under Armour is widely perceived as a locker-room brand that resonates most with suburban boys," Sara Germano writes at The Wall Street Journal. "It is a good place to start, but to see bigger sales Under Armour will have to gain clout among urban retailers and the fashion-focused crowd."